This invention relates to particulate carriers for functional substances. More particularly, this invention is directed to particle aggregates having high porosity and a large intraaggregate reticulate volume for containment of functional substances. The present aggregate compositions are economically manufactured to have predetermined release characteristics and other desired physical properties.
There has been a significant research and development effort directed to the definition and manufacture of carriers for functional substances for a wide variety of commercial applications. Ideal carrier compositions are those that inherently exhibit high capacity for carrying/containment of functional substances, those which work to enhance or prolong the functionality of the contained or carried substance, and those which can be economically manufactured to meet the unique specifications required for each targeted application. Such are the characteristics of the composition of the present invention.
In accordance with this invention, there is provided a versatile, low cost porous composition having a high void volume and thus a high capacity for containment for functional substances. The composition comprises free flowing aggregates of discrete particles, most preferably starch granules, bound together with a binder at their points of contact in the aggregate. The use of starch granules as the particle component of the present carrier composition provides surprisingly uniform spherical aggregates ranging in diameter from about 15 to about 150 microns, depending on the size distribution of the component starch granules. The surfaces of the aggregated particles cooperate to define an intraaggregate reticular volume for releasable containment of the functional substances. Advantageously the physical/chemical characteristics of the composition can be readily adjusted to meet the functional requirement of each targeted application by selection of the particle and binder components.
The particle aggregate compositions in accordance with this invention are prepared by forming a suspension of the particulate component in a solution of a binder and spray-drying the resulting suspension utilizing art-recognized spray drying equipment/technology. The particulate components can be pre-treated to promote their compatibility with the targeted functional substance and to impart other properties such as hardness and solubility characteristics appropriate for the contemplated carrier application. Further, the binder, typically a polymeric material exhibiting affinity for the particle component, can be selected according to its chemical and physical characteristics to optimize functionality of the particulate aggregates as a carrier in a targeted application. Thus the binder component can be selected with view of its solubility, its chemical reactivity, for example, its bioerodability or biodegradability, as appropriate to optimize functionality of the particle aggregates of the invention. Finally, the present aggregate compositions can be coated to provide additional functionality.
Functional substances can be easily introduced into the reticular volume of the present porous aggregates. The high intraaggregate reticular volume and high internal surface area of the present aggregate compositions allow high loading of functional substances. The loaded porous aggregate compositions of this invention are free flowing powders which facilitate handling and mixing of the functional substance in product formulations and further provides a matrix for sustained or prolonged release of the carried functional substance. Additionally, it is contemplated that the particle aggregates in accordance with this invention will exhibit functionality independent of their use as a carrier for functional substances. Thus, they may be used in prepared foods that require minute gritty character, either in mouth feel or in appearance. The particle aggregate composition in accordance with this invention has utility in the areas of food/nutrition, the preparation of topical creams and lotions, deodorant/antiperspirants, cosmetics, agricultural products, and products for human and veterinary medicine. The present compositions can be designed to enhance and prolong the functional characteristics of contained functional compositions. Alternatively, the present composition can function to protect the contained functional substance from premature degradation. For example, orally administered pharmaceutical compositions can be formulated with/in the aggregate compositions, preferably the granular starch-based compositions of this invention, to provide an enteric formulation which functions to protect the active substance from the acid/digestive conditions of the stomach and thereafter release the active substance in the small intestine.